Ferrule holder assembly for optical-fiber-end-face grinding apparatus

ABSTRACT

A ferrule holder assembly for an optical-fiber-end-face grinding apparatus comprises a ferrule holder board supported to be moved upward and downward in parallel with a grinding board of the optical-fiber-end-face grinding apparatus, a ferrule sleeve provided at the ferrule holder board for receiving and supporting an optical fiber ferrule while putting the tip at the grinding board, an adapter for retaining the optical fiber ferrule or a connector for supporting the optical fiber ferrule in a state where the optical fiber ferrule is inserted into the ferrule sleeve, and an urging unit for urging the adapter in a direction opposite to the grinding board from the ferrule holder board.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a ferrule holder assembly for anapparatus for grinding end faces of a plurality of ferrules with opticalfibers simultaneously.

[0003] 2. Description of the Related Art

[0004] It is well known by those skilled in the art that in order toconnect optical fibers together while reducing connection loss andreflected returned light, tips of ferrules are ground by perpendicularor inclined spherical grinding to connect the optical fibers together.The shape of the convex spherical surface in this case is standardizedby the international standard (IEC: International ElectrotechnicalCommission No. 60874-14-6) or the like. U.S. Pat. No. 5,351,445discloses a technique of apparatus for grinding end faces of a pluralityof optical fibers simultaneously. A ferrule holder of this grindingapparatus projects tips of ferrules from a plurality of insertion holes(sleeves) thereof to a grinding board by a specified amount and supportsthe ferrules. Grinding is performed by revolving a grinding film put onan elastic plate of the grinding board by an autorotational and orbitalmotion mechanism of the grinding apparatus and applying a specifiedamount of pressure to a grinding jig on which a plurality of ferruleswith the optical fibers are mounted. Thus, the shape of the tips of theferrules of the optical fibers can be made convex spherical surface thatsatisfies the standard.

[0005] Even if a similar type of ferrule or connector is used, however,variation in length exists within a dimensional tolerance and the sizediffers depending on the manufacturer. Therefore, when a plurality offerrules or connectors are mounted on the ferrule holder, it isdifficult that all the tips of the ferrules are projected by a specifiedamount and supported.

[0006] Although a reference plane of the ferrule holder for mounting theferrule for grinding is processed to have a specified height with astrict tolerance, since the reference plane for mounting the pluralityof ferrules is fixed, the heights of the tips of the ferrules from theinsertion holes vary by an amount of variation in length of ferrules orhousings of the ferrules.

[0007] When the plurality of end surfaces of the optical fiberconnectors of a lot in which the lengths of ferrules vary aresimultaneously ground, since the grinding holder is directly weighted inthe conventional grinding apparatus, problems occur in that the holderis tilted due to the variation in projection amount therefrom togenerate a deviation from the shaft axis, or the ferrules having a smallprojection amount are insufficiently ground. Therefore, in the method ofthe conventional grinding apparatus, it is necessary to performpreliminary grinding up to a shortest ferrule and then to performgrinding again from a state in which the ferrules have the same height.

SUMMARY OF THE INVENTION

[0008] Accordingly, it is an object of the present invention to providea ferrule holder assembly for an optical-fiber-end-face grindingapparatus in which the aforesaid problems of the variation in length ofthe housings of the ferrules can be solved.

[0009] In order to achieve the above objects, a ferrule holder assemblyfor an optical-fiber-end-face grinding apparatus according to thepresent invention includes a ferrule holder board provided to be movedupward and downward in parallel with a grinding board of theoptical-fiber-end-face grinding apparatus, a ferrule sleeve provided atthe ferrule holder board for receiving and supporting an optical fiberferrule while putting the tip thereof at the grinding board, an adapterfor retaining the optical fiber ferrule or a connector for supportingthe optical fiber ferrule in a state in which the optical fiber ferruleis inserted into the ferrule sleeve and urging means for urging theadapter in a direction to the grinding board from the ferrule holderboard.

[0010] The adapter retains and supports the optical fiber ferrule or theconnector for supporting the optical fiber ferrule at the ferrule holderboard in such a manner that the ferrule can be slid to the ferrulesleeve in the axial direction thereof, its revolution is restricted, andthe downward movement limit is specified relative to said ferrule holderboard.

[0011] A retaining part of the adapter has a hook structurecorresponding to a retaining member of a plug-type optical fiberconnector housing.

[0012] A retaining part of the adapter has a screw structurecorresponding to a retaining member of a plug-type optical-fiberconnector housing.

[0013] The ferrule holder assembly for the optical-fiber-end facegrinding apparatus is a ferrule holder assembly for an optical-fiber-endface grinding apparatus for inclined grinding, the attaching angle ofsaid adapter is the same as that of the ferrule sleeve, and a guide keygroove of the adapter is formed only at one side.

[0014] The urging means is a coil spring and the force of the spring issmaller than the urging force of springs assembled to the connector plugitself.

[0015] The means for urging the adapter to the holder is a coil springand the weight is 550 gf or less appropriate for spherical grinding. Theferrule holder assembly for the optical-fiber-end-face grindingapparatus according to the present invention includes adapters in eachof which the ferrule or the housing is fixed to a grinding-jig-platemain body thereof having a plurality of insertion holes penetrated forreceiving the outside diameter of the tip of the ferrule. By pressingthe adapter with a spring pressure, the ferrule with the optical fibercan apply a specified pressure toward a grinding board.

[0016] In this case as well, although the heights of the tips of theferrules from the plurality of insertion holes vary, the pressure of thetips of the ferrules to the grinding board can be almost the same bysetting a spring constant of a spring that presses the adapter small inspite of the variation in the ferrules and the housing, and thereby thevariation can be absorbed. Thus, the variation in the shape of the tipsof the plurality of ferrules after grinding can be reduced.

[0017] In addition, even in the inclined spherical grinding, thevariation can be reduced by providing the insertion hole of thegrinding-jig-plate main body in a manner so as to be inclined relativeto the grinding surface, and also by inclining the adapter having amechanism to be pressed by the spring pressure.

[0018] The object to be ground is not limited to the ferrule, butvarious kinds of connectors can be applied depending on the design ofthe adapter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a plan view of an embodiment of a ferrule holderassembly for an optical-fiber-end-face grinding apparatus according toan embodiment of the present invention;

[0020]FIG. 2 is a front view of the optical-fiber-end-face grindingapparatus on which the ferrule holder assembly shown in FIG. 1 ismounted;

[0021]FIG. 3 is an enlarged view showing a state in which an SC-typeoptical fiber connector is attached to the embodiment of the ferruleholder assembly for the optical-fiber-end-face grinding apparatus shownin FIG. 1;

[0022]FIG. 4 is an enlarged plan view showing a state in which anoptical fiber connector is not connected to the embodiment of theferrule holder assembly for the optical-fiber-end-face grindingapparatus shown in FIG. 1;

[0023]FIG. 5 is an enlarged cross-sectional view showing a state inwhich the optical fiber connector is not connected to the embodiment ofthe ferrule holder assembly for the optical-fiber-end-face grindingapparatus shown in FIG. 1;

[0024]FIG. 6 is a cross sectional view of another embodiment (forinclined grinding) of the ferrule holder assembly for theoptical-fiber-end-face grinding apparatus according to the presentinvention;

[0025]FIG. 7 is a cross sectional view showing a state in which aconnector is connected to a still another embodiment (for grindingferrules of an LC-type connector) of the ferrule holder assembly for theoptical-fiber-end-face grinding apparatus according to the presentinvention;

[0026]FIG. 8 is a cross sectional view of a further another embodiment(for grinding ferrules of an ST-type connector) of the ferrule holderassembly for the optical-fiber-end-face grinding apparatus according tothe present invention;

[0027]FIG. 9 is a cross sectional view of a still further anotherembodiment (for grinding ferrules of an FC-type connector plug) of theferrule holder assembly for the optical-fiber-end-face grindingapparatus according to the present invention; and

[0028]FIG. 10 is a cross sectional view of a yet further anotherembodiment (a ferrule with a flange) of the ferrule holder assembly forthe optical-fiber-end-face grinding apparatus according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Embodiments of the ferrule holder assembly for theoptical-fiber-end-face grinding apparatus according to the presentinvention will be described hereinbelow with reference to the drawings.FIG. 1 is a plan view of an embodiment of the ferrule holder assemblyfor the optical-fiber-end-face grinding apparatus according to thepresent invention. Adapters 2 for supporting 20 units of connectorferrules, the number of which corresponds to the number of the connectorferrules, are arranged round a concentric circle on a ferrule holderboard 1 having a generally square shape, in which a circular hole isprovided at the center. This ferrule holder assembly for theoptical-fiber-end-face grinding apparatus is mounted on theoptical-fiber-end-face grinding apparatus as shown in FIG. 2. A grindingapparatus main body 12 is provided with a grinding board 13 revolving onits axis and the orbit, on which a grinding film 14 is mounted.

[0030] Holder retaining stands 15 are provided at the upper four cornersof the grinding apparatus main body 12, into which a holder retainingshaft 17 urged downwardly is respectively inserted in the centerthereof.

[0031] When the ferrule holder board 1 is mounted, levers of the holderretaining shafts are each rotated so as to apply a strong force.

[0032] Holder-mounting reference surfaces 16 at the upper four surfacesof the holder retaining stands 15 are the same surface and are set to beparallel to a grinding surface of the grinding board. The height is setto L₂(mm) from the grinding surface. The motion of the grinding board ofthe grinding apparatus is preferably a combined motion of therevolutions on its axis and the orbit; however, only an ordinaryrotation is also possible.

[0033]FIG. 3 is an enlarged view showing a state in which an SC-typeoptical fiber connector is attached to the embodiment of the ferruleholder assembly for the optical-fiber-end-face grinding apparatus shownin FIG. 1. FIG. 4 is an enlarged plan view showing a state in which anoptical fiber connector is not connected to the embodiment of theferrule holder assembly for the optical-fiber-end-face grindingapparatus shown in FIG. 1. FIG. 5 is an enlarged cross-sectional viewshowing a state in which the connector is not connected as well. Asshown in FIG. 5, recessed portions are formed in the ferrule holderboard 1, corresponding to each connector retaining position, and aferrule sleeve 1 a of the holder board is provided at the centerthereof, respectively.

[0034] The adapter 2 has a quadrangular cylinder shape and is insertedinto the recessed portion in a manner so as to enclose the ferrulesleeve 1 a as shown in FIGS. 4 and 5. A pair of key grooves 2 b and 2 bfacing each other are formed at the side of the adapter 2. In addition,a pair of adapter hooks 2 a are provided at the inside of the adapter 2,for retaining an SC-type connection plug that will be described later.An end of the adapter hook 2 a is inclined, and the adapter hook 2 a iselastically widened in response to insertion of the SC-type connectionplug, and is then restored at a predetermined position to retain a plugbody 11 of the SC-type optical fiber connector as shown in FIG. 3. Partof the walls at the short sides of the adapter 2 are removed at thelower sides, and a pair of adapter flanges (spring bearings) 2 c forbearing a spring are provided thereat. A pair of adapter-spring pressingplates 4 are fixed to the ferrule holder board 1 using screws 6 in sucha manner that the innermost ends of the plates overlie the upper sidesof the pair of adapter flanges (spring bearings) 2 c. A pair of adaptersprings 5 is inserted therebetween so as to urge the adapter 2downwardly.

[0035] A ferrule 9 of the SC-type optical fiber connector plug isinserted between a plug body 11 and a flange 9 a so as to be urged in aprojecting direction by springs 10. An optical fiber cord, the tip ofwhich is adhered to the ferrule 9, is led to the outside through a hood7 covering the plug body 11. The operator holds a connector housing(pick-up portion) 8 that is provided separately from the plug body 11 toperform attaching/detaching operations to the adapter.

[0036] The plurality of optical fiber ferrules are attached to theembodiment of the ferrule holder assembly for the optical-fiber-end-facegrinding apparatus shown in FIG. 1, and circular cutout portions forpositioning at four corners of the ferrule holder board 1 are adjustedto the holder retaining stands 15 of the grinding apparatus, and thenthe holders are each sufficiently tightened by the holder retainingshaft 17 by rotating the mounting lever.

[0037] In this instance, if the projection amount L₁ of the ferrule fromthe lower end surface of the ferrule holder board 1 is set to an amountlarger than a distance L₂ from the lower end surface of the ferruleholder board 1 to a surface of the grinding film, the tip of the ferruleis pressed up by the grinding film in a state in which the ferruleholder board 1 is tightened, and thereby the force of the adapter spring5 is applied to the end face of the ferrule. Grinding is performed inthis state.

[0038] When the grinding amount is 0.1 mm or less, the grinding ispossible where L₁−L₂>0.1 mm; however, the features of the presentinvention is that even when the length of the ferrules varies, there isno need for adjustment particularly. Assuming that the variation in thelength of the ferrules is 0.2 mm, a grinding margin of 0.1 mm can beassured even for the shortest ferrule where L₁−L₂>0.3 mm. The force ofthe coil spring 5 applied to the adapter is preferably 550 gf or less inthe case of spherical grinding using an elastic material plate as thegrinding board, and the spring characteristic is preferably within theabove-mentioned variation, having no influence on the force.

[0039] The above-described embodiment is an example of perpendicularlygrinding of the tip of the ferrule together with the optical fiber. Theferrule holder assembly for the-optical-fiber-end-face grindingapparatus for inclined spherical grinding of the tip of the ferrule canbe provided. FIG. 6 is a cross sectional view of a ferrule holderassembly for the inclined grinding. A hole for inserting the adapter 2is processed to be inclined corresponding to the grinding angle. The keygroove 2 b for positioning in this case should be provided only at apredetermined side.

[0040]FIG. 7 is a cross sectional view showing a state in which aconnector is connected to another embodiment (for grinding the ferruleof an LC-type connector) of the ferrule holder assembly forthe-optical-fiber-end-face grinding apparatus according to the presentinvention. An LC-type connector plug 20 is provided with a retaininghook lever 21, and a projection provide at the lever 21 is engaged witha projection at the inner surface of the adapter 2 so as to fix theLC-type connector plug 20 to the ferrule holder board. An optical fibercord (not shown) is led out through a hood 27. In the drawing,description of the construction described previously with reference toFIG. 3 is omitted by giving common numerals or symbols. The same shallalso apply to FIGS. 8, 9, 10.

[0041]FIG. 8 is a cross sectional view of another embodiment (forgrinding a ferrule of an ST-type connector plug) of the ferrule holderassembly of the optical-fiber-end-face grinding apparatus according tothe present invention. The ST-type connector plug 30 is provided with akey pin 31 at the adapter 2. The key pin has a cylinder 32 of theST-type connector plug 30 connected thereto with a bayonet.

[0042]FIG. 9 is a cross sectional view of another embodiment (forgrinding a ferrule of an FC-type connector plug) of the ferrule holderassembly of the optical-fiber-end-face grinding apparatus according tothe present invention. The FC-type connector plug 40 can be retained tothe adapter with a box nut 42.

[0043]FIG. 10 is a cross sectional view of another embodiment (a ferrulewith a flange) of the ferrule holder assembly of theoptical-fiber-end-face grinding apparatus according to the presentinvention. This is a case of grinding the ferrule (a single body) 9 withthe flange 9 a, which can be retained to the adapter with a box nut 51.

[0044] As described above in detail, in the grinding apparatus using theassembly according to the present invention, the projection amount ofthe ferrule is made the same in a state in which the assembly isattached to the grinding apparatus within a variation in the projectionamount by disposing a separate spring to each adapter. That is, even ifthe lengths of the ferrules varies, grinding can be performed withoutpreliminary grinding, and as a result, uniform grinding can be performedfor a short time without unnecessary labor. In addition, attaching theconnector to the adapter facilitates the attachment/detachment,resulting in an improved workability.

What is claimed is:
 1. A ferrule holder assembly for anoptical-fiber-end-face grinding apparatus, comprising: a ferrule holderboard provided to be moved upward and downward in parallel with agrinding board of the optical-fiber-end-face grinding apparatus; aferrule sleeve provided at said ferrule holder board for receiving andsupporting an optical fiber ferrule while putting the tip thereof at thegrinding board; an adapter for retaining the optical fiber ferrule or aconnector for supporting said optical fiber ferrule in a state in whichsaid optical fiber ferrule is inserted into said ferrule sleeve; andurging means for urging said adapter in a direction to said grindingboard from said ferrule holder board.